A fuel cell is a device that converts chemical energy from a fuel into electricity through a chemical reaction of positively charged hydrogen ions with oxygen or another oxidizing agent. The fuel cell can produce electricity continuously for as long as fuel and oxygen or air are supplied continuously. Particularly, a planar solid oxide fuel cell is more popular in various applications because it has advantages of durable stability and low production cost and because a plurality of the planar solid oxide fuel cells may be stacked and electrically connected in series to produce high voltage.
However, in a stack of the conventional planar solid oxide fuel cells, the power efficiency and stability thereof may be negatively affected due to the fact that deformation of a seal material used for stacking the planar solid oxide fuel cells may affect flow of a fuel fluid and/or that the seal material may come into contact with the fuel fluid to react with the fuel fluid or to be eluted by the fuel fluid. In addition, it is desirable in the art to provide a solid oxide fuel cell having enhanced power density, fuel utilization, and power efficiency.